Detection Frequency Analysis Research Articles

Chemometrics and sensomics-assisted identification of key odorants responsible for retort odor in shelf-stored green tea infusion: A case study of Biluochun

The deterioration of aroma quality in tea beverages during the shelf life is a significant issue. In this study, sensomics techniques were employed to identify the characteristic factor contributing to aroma degradation in green tea infusion. Samples A (no/faint retort odor) and B (high intensity retort odor) were selected based on their retort-like odor intensity after heat treatment simulating shelf-life conditions. The key odorants were identified through a combination of chemometrics analysis, comparative aromatic extract dilution analysis (cAEDA), detection frequency analysis (DFA), and odor-specific magnitude estimation (OSME). Subsequently, eight odorants, including linalool (892.451 μg/L), (E)-β-damascenone (5.105 μg/L), phenylacetaldehyde (27.720 μg/L), nonanal (2201.439 μg/L), α-terpineol (7.166 μg/L), geraniol (0.499 μg/L), theaspirane (0.044 μg/L), and 2-hydroxy-5-methylacetophenone (2.973 μg/L), were identified as the key substances contributing to the retort-like odor in sample B. Aroma recombination and omission test further demonstrated that elevated concentrations of nonanal, geraniol, phenylacetaldehyde, and theaspirane might be the primary reasons for the retort odor observed in samples.

Profiling the Major Aroma-Active Compounds of Microwave-Dried Jujube Slices through Molecular Sensory Science Approaches.

To discriminate the aroma-active compounds in dried jujube slices through microwave-dried treatments and understand their sensory attributes, odor activity value (OAV) and detection frequency analysis (DFA) combined with sensory analysis and analyzed through partial least squares regression analysis (PLSR) were used collaboratively. A total of 21 major aromatic active compounds were identified, among which 4-hexanolide, 4-cyclopentene-1,3-dione, 5-methyl-2(5H)-furanone, 4-hydroxy-2,5-dimethyl-3(2H)furanone, 3,5-dihydroxy-2-methyl-4-pyrone were first confirmed as aromatic compounds of jujube. Sensory evaluation revealed that the major characteristic aromas of dried jujube slices were caramel flavor, roasted sweet flavor, and bitter and burnt flavors. The PLSR results showed that certain compounds were related to specific taste attributes. 2,3-butanedione and acetoin had a significant positive correlation with the roasted sweet attribute. On the other hand, γ-butyrolactone, 4-cyclopentene-1,3-dione, and 4-hydroxy-2,5-dimethyl-3(2H)furanone had a significant positive impact on the caramel attributes. For the bitter attribute, 2-acetylfuran and 5-methyl-2(5H)-furanone were positively correlated. Regarding the burnt flavor, 5-methyl-2-furancarboxaldehyde and 3,5-dihydroxy-2-methyl-4-pyrone were the most influential odor-active compounds. Finally, 2-furanmethanol and 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one were identified as the primary sources of the burnt and bitter flavors. Importantly, this work could provide a theoretical basis for aroma control during dried jujube slices processing.

Characterization of key aroma compounds in melon spirits using the sensomics concept

Processing melon into spirits has important environmental and economic value. However, the flavour of melon spirits is undesirable and has yet to be studied. In this study, a combination of odour activity value, gas chromatography–olfactometry detection frequency analysis, aroma reconstitution, and omission tests showed that key aroma compounds (Group 1), including 3,6-nonadien-1-ol and 3-nonen-1-ol, were responsible for the undesirable green and fatty aromas of melon spirits. Meanwhile, the desirable fruity and floral aromas were provided by Group 2 compounds, which included isoamyl acetate and (E)-damascenone. Omission tests of Group 1 and Group 2 compounds showed that, similar to the fruit and floral aromas, the green and fatty aromas were important components of melon spirit flavour. Furthermore, adding Group 2 compounds to the spirits inhibited green and fatty flavours, improved the fruit and floral aromas, and enhanced the sensory evaluation of melon spirits. This study provides a basis for improving the production process and aroma of melon spirits.

An Insight by Molecular Sensory Science Approaches to Contributions and Variations of the Key Odorants in Shiitake Mushrooms

An insight using molecular sensory science approaches to the contributions and variations of the key odorants in shiitake mushrooms is revealed in this study. Odorants were extracted by headspace solid phase microextraction (HS-SPME) and direct solvent extraction combined with solvent-assisted flavor evaporation (DSE-SAFE) in fresh and hot-air-dried shiitake mushrooms. Among them, 18 and 22 predominant odorants were determined by detection frequency analysis (DFA) and aroma extract dilution analysis (AEDA) combined with gas chromatography-olfactometry (GC-O) in the fresh and dried samples, respectively. The contributions of these predominant odorants in the food matrix were determined by quantification and odor activity values (OAVs) with aroma recombination verification. There were 13 and 14 odorants identified as key contributing odorants to overall aroma, respectively. 1-Octen-3-ol and 1-octen-3-one were the most key contributing odorants in the fresh samples in contributing mushroom-like odor. After hot-air-drying, the OAV and concentrations on dry basis of the key contributing odorants changed, due to oxidation, degradation, caramelization and Maillard reactions of fatty acids, polysaccharides and amino acids. 1-Octen-3-ol was reduced most significantly and degraded to 1-hydroxy-3-octanone, while phenylethyl alcohol increased the most and was formed by phenylalanine. In hot-air-dried samples, lenthionine became the most important contributor and samples were characterized by a sulfury odor. Overall contributions and variations of odorants to the aroma of shiitake mushrooms were revealed at the molecular level.

Insights into the major aroma-active compounds in clear red raspberry juice (Rubus idaeus L. cv. Heritage) by molecular sensory science approaches

The major aroma-active compounds in clear red raspberry juice were identified by molecular sensory science approaches. Thirty-one aroma-active compounds were identified using detection frequency analysis and aroma extract dilution analysis. Among them, 18 volatiles with aroma activity in red raspberry were identified for the first time, while 14 volatiles with odor activity values (OAVs) ≥ 1 were confirmed as the major aroma-active compounds. Three C6 aldehydes showed the highest detection frequencies of 8, and β-ionone exhibited the highest OAV of 9507 and flavor dilution factor of 512, which indicated that the floral and grassy note could be dominant in overall aroma. Quantitative descriptive analysis suggested that the grassy, floral, woody, and caramel-like notes can be simulated using aroma recombination model 1. Electronic nose analysis also demonstrated that model 1 had closer similarity to the original juice than others. The combination strategy used here would help improve the knowledge of red raspberry aroma.

Key Aroma Compounds of Dark Chocolates Differing in Organoleptic Properties: A GC-O Comparative Study.

Dark chocolate samples were previously classified into four sensory categories. The classification was modelled based on volatile compounds analyzed by direct introduction mass spectrometry of the chocolates’ headspace. The purpose of the study was to identify the most discriminant odor-active compounds that should characterize the four sensory categories. To address the problem, a gas chromatography-olfactometry (GC-O) study was conducted by 12 assessors using a comparative detection frequency analysis (cDFA) approach on 12 exemplary samples. A nasal impact frequency (NIF) difference threshold combined with a statistical approach (Khi² test on k proportions) revealed 38 discriminative key odorants able to differentiate the samples and to characterize the sensory categories. A heatmap emphasized the 19 most discriminant key odorants, among which heterocyclic molecules (furanones, pyranones, lactones, one pyrrole, and one pyrazine) played a prominent role with secondary alcohols, acids, and esters. The initial sensory classes were retrieved using the discriminant key volatiles in a correspondence analysis (CA) and a hierarchical cluster analysis (HCA). Among the 38 discriminant key odorants, although previously identified in cocoa products, 21 were formally described for the first time as key aroma compounds of dark chocolate. Moreover, 13 key odorants were described for the first time in a cocoa product.

Characterization of the major aroma-active compounds in Keitt mango juice: Comparison among fresh, pasteurization and high hydrostatic pressure processing juices

The commercial mango cultivar Keitt lacks a theoretical foundation for aroma control during processing. To discriminate the aroma-active compounds in fresh mango juice, odor activity value (OAV) and detection frequency analysis (DFA) were used collaboratively. A total of 12 components were identified as major aroma-active compounds, among which 2,4-dimethylstyrene was firstly confirmed as an aroma compound in mango. The changes of aromatic compounds during pasteurization and high hydrostatic pressure (HHP) sterilization were further studied. Quantitative descriptive analysis (QDA) was applied to validate the sensory differences. Principal component analysis (PCA) based on aroma compound variation coincided with the overall note. QDA demonstrated that fresh mango juice was the most accepted, followed by HHP and pasteurized juices. The finding might be well correlated with the differences in 6 odor notes. This work would help to better understand and control the critical aroma determinants for mango juice processing.

Identification of Different Pink Pomelo Varieties by Gas Chromatography-mass Spectrometry and Olfactometry Coupled to Chemometrics

To differentiate different kinds of pink pomelos, which came from the main producing area of pink pomelo varieties in China, headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry and olfactometry (GC-MS-O) was used to determinate and characterize volatile profiles of different varieties. Olefins, alcohols, ketones represented the most abundant volatile compounds in all varieties of pink pomelo juices. There are 38 aroma-active compounds perceived by the trained panel of judges by using detection frequency analysis method (DFA). Principal components analysis (PCA) combining GC-MS analysis was applied and successfully distinguished six varieties of pink pomelo juices from four different geographical regions of China, which is in accordance with their vegetal sampling location. Further, partial least squares-discriminant analysis (PLS-DA) indicated that this model is good in correlating citrus odor. Decanal, hexan-1-ol, γ-selinene could be identified as the main characteristics to distinguish different varieties.

Aroma characterization of freshly‐distilled French brandies; their specificity and variability within a limited geographic area

AbstractFreshly‐distilled French wine brandies were evaluated by gas chromatography‐olfactometry (GC‐O). Six brandy samples were studied, coming from two growth areas, both belonging to the same limited geographic zone, which is a homogeneous vineyard area. The GC‐O methodology, using detection frequency analysis, revealed 88 olfactive areas (OAs) for which the detection frequency was ≥ 25%. OAs were then identified using gas chromatography‐mass spectrometry in electron and chemical ionization modes and semi‐quantified by internal normalization using gas‐chromatography with flame ionization detection. Co‐eluting species were separated by multidimensional gas chromatography‐mass spectrometry/olfactometry (MDGC‐MS/O). Eleven new molecules were tentatively identified for the first time in brandy, as impact odorant compounds: ethyl prop‐2‐enoate, 2‐furfuryl formate, 1,2,4,5‐tetramethylbenzene, (Z)‐ocimenol, 1,4,6‐trimethyl‐1,2‐dihydronaphthalene, 2‐ethoxybenzyl alcohol, 2‐ethylhexanoic acid, 2‐phenoxyethanol, 4‐hydroxy‐3‐methylacetophenone, 4‐(2,3,6‐trimethylphenyl)butan‐2‐one and 2,3‐dihydrofarnesol. Composition and perception differences between samples according to their origin were investigated. Statistical analyses on OA detection frequencies and semi‐quantitative data were used to distinguish the samples. A lot of variables appeared to be common to all spirits, and may represent an aromatic background for the brandies, characteristic of the geographic zone. Although a few particular OAs were found more relevant in particular samples, no growth area‐specific compound was identified. Therefore, differences between spirits are more likely due to an aromatic balance between concentrations of a set of common molecules, among which ethyl esters and alcohols played a prominent role, rather than the presence of specific compounds with unique aromas. Copyright © 2016 John Wiley & Sons, Ltd.

Characterization of aroma-active volatiles in three Chinese bayberry (Myrica rubra) cultivars using GC–MS–olfactometry and an electronic nose combined with principal component analysis

Chinese bayberry (Myrica rubra Sieb. et Zucc.) is one of the most popular and valuable fruits in China because of its unique and exquisite flavor. In this study, headspace solid-phase micro-extraction (HS-SPME) coupled with gas chromatography–mass spectrometry and olfactometry (GC–MS–O) analyses were used to characterize the aroma-active profiles of the fruits from three different bayberry cultivars. The aim was to differentiate the bayberry cultivars by their aroma. Fifty-five volatile components, composed of aldehydes (10), alcohols (9), esters (8), terpenes (17), and others (11), were identified by optimized HS-SPME/GC–MS. Meanwhile, 36 aroma-active compounds were detected by olfactometry using detection frequency analysis (DFA). Hexanal (grass-like), (E)-2-hexenal (green), nonanal (fruit, flower), 1-hexanol (flower), and isocaryophillene (wood) were identified in all three cultivars. Further principal component analysis (PCA) of the active aromas revealed their contributions to the odor differences among the bayberry cultivar groups. The BQ bayberry was characterized by having a stronger “herb” odor, which is mainly caused by benzoic acid and methyl ester. DK bayberry had a stronger “grass” odor, which is mainly caused by 2,6-dimethyl-2,4,6-octatriene, while FHZ bayberry had a stronger “pine” odor, which is caused mainly by α-pinene. The GC–MS–O and electronic nose techniques, when combined with PCA, could be used to successfully distinguish between different bayberry cultivars.

Characterization of Aronia melanocarpa Volatiles by Headspace-Solid-Phase Microextraction (HS-SPME), Simultaneous Distillation/Extraction (SDE), and Gas Chromatography-Olfactometry (GC-O) Methods

The profiles of volatile constituents of berry fruit of two Aronia melanocarpa genotypes were evaluated by headspace-solid-phase microextraction (HS-SPME), simultaneous distillation and extraction (SDE), and gas chromatography-olfactometry (GC-O). In total, 74 volatile compounds were identified in chokeberry juice, 3-penten-2-one, 3,9-epoxy-p-menth-1-ene, and benzaldehyde being the most abundant constituents; however, their percentage concentrations were remarkably different in the HS-SPME and SDE profiles. Twenty two aroma-active compounds were detected and characterized by the trained panelists in HS-SPME using GC-O detection frequency analysis. Olfactometry revealed that ethyl-2-methyl butanoate, ethyl-3-methyl butanoate, ethyl decanoate ("fruity" aroma notes), nonanal ("green" notes), unidentified compound possessing "moldy" odor, and some other volatiles may be very important constituents in formation of chokeberry aroma of both analyzed plant cultivars.

Geographical origin identification of propolis using GC–MS and electronic nose combined with principal component analysis

Dynamic headspace sampling (DHS) coupled with gas chromatography–mass spectrometry and olfactometry (GC–MS–O) analysis have been applied for the determination of the characteristic volatile profile of propolis with the aim to differentiate the propolis from different regions of China. Acids, esters, alcohols, terpenes, aromatics represented the most abundant compounds in propolis among the ninety-nine volatile components identified by comparing with mass spectra and retention indices (RI) or from literature. In addition, principal component analysis (PCA) based on the data of DHS–GC–MS and electronic nose was used to study and obtain the important volatile compounds contributed to the differentiation of the propolis samples from different regions. Furthermore, a total of 28 odor-active compounds were detected and characterized by the trained panel of judges in the sniffing port of GC–O by using detection frequency analysis (DFA). In conclusion, GC–MS analysis and electronic nose combining with PCA could successfully distinguish the twelve representative raw propolis samples from 4 different geographical regions of China. The samples have been assigned to four large groups in accordance with their vegetal sampling location and we also have observed the volatile compounds resulting in the odor differentiation.

An original approach for gas chromatography-olfactometry detection frequency analysis: Application to gin

Gas Chromatography-Olfactometry (GC-O) is a technique that lies halfway between physicochemical and sensory analysis and involves the perception of volatile flavour compounds, separated by gas chromatography, by the human nose. Of the different GC-O procedures available, detection frequency has been proved to be more rapid and more repeatable, even with an untrained panel. This characteristic regarding the panel is often not considered when dealing with the sensory attributes determined by assessors.An original approach to GC-O using the detection frequency procedure has been developed and tested on two types of gin and made it possible to benefit from sensory data. The panel consisted in 10 assessors (five male and five female) with prior GC-O experience. They generated odour events each time they perceived an odour. In addition, they were asked to provide as precise a description as possible of the smell they perceived. The 2589 odour events thus generated were then grouped into 209 odorant areas using a specially-developed software, based on the closeness of their linear retention indices. These odorant areas were then associated with compounds identified using Gas Chromatography Mass-Spectrometry. The intensity of a compound was defined as the number of odour events in the corresponding odorant area. Thirty height compounds, mostly terpenoids, were identified as having an impact on gin aroma and enabled differentiation of the two products. Among these 38 compounds, those belonging to the two products were described as constituting a “gin base”, while the others were described as “typical compounds”. This procedure also enabled the identification of compounds whose perceived intensity was highly sensitive to changes in concentration. Finally, an odour classification wheel was developed to categorise the descriptors obtained in 12 supercategories. An odour profile was generated for each odorant area, based on the occurrence of a descriptor in a supercategory. These odour profiles were either homogeneous (with one dominant odour) or heterogeneous (with no dominant odour). This approach enabled a quantitative sensory description of the odorant areas generated by GC-O.

Characterisation of volatile compounds of lupin protein isolate‐enriched wheat flour bread

The influence of lupin protein isolate (LPI) on the volatile fraction of wheat flour (WF) bread was investigated. Headspace solid-phase microextraction technique (HS-SPME) coupled to the gas chromatography–mass spectrometry (GC–MS) analysis was applied to characterise volatile compounds of both crust and crumb. In a preliminary sensory experiment, LPI was found to have a modifying effect on the odour of WF-bread. The most important odorants of WF and LPI-containing wheat flour (LWF) breads were evaluated on the basis of detection frequency analysis. Fifty three compounds were detected by more than five judges, ten of which were detected only in LWF bread. The most important compounds of LPI-containing crumb and crust were vinylpyrazine, hexanal, 2-propylpyrazine, 2-octenal, 2,3-butanedione, 2,5-dimethylpyrazine, non-identified compounds with green, mushroom-like or pleasant odour and pyrazines. Their presence was attributed either to oxidative degradation of fatty acids or thermal reactions. Most of these compounds contributed to the aroma character of LPI-bread with green, earthy, malty, buttery and roasted notes.

Identification of Aroma-Active Compounds in Jiashi Muskmelon Juice by GC-O-MS and OAV Calculation

To identify aromatic compounds in Jiashi melon juice, gas chromatography-mass spectrometry-olfactometry (GC-MS-O) analysis was used. Odor activity values (OAVs) were also calculated on the basis of the qualitative and quantitative analysis of volatile compounds. Results showed that 42 volatiles were identified, among which 4 compounds, namely, diethyl carbonate, isophorone, 2-butoxyethyl acetate, and menthol, were identified or tentatively identified for the first time as volatiles in melon fruit. Twelve compounds, namely, (2E,6Z)-nona-2,6-dienal, (3Z,6Z)-nona-3,6-dien-1-ol, ethyl butanoate, ethyl 2-methylbutyrate, ethyl 2-methylpropanoate, (Z)-non-6-enal, (E)-2-nonenal, heptanal, methyl 2-methylbutyrate, nonanal, hexanal, and 2-methylpropyl acetate, were identified as the potent odorants of Jiashi melon juice by both OAV and detection frequency analysis (DFA). In addition, seven odorants were detected by all of the panelists and showed higher OAVs, indicating that DFA and OAV resulted in relatively similar "Jiashi" melon aroma patterns.

Chemical and sensory characterisation of aroma of Viburnum opulus fruits by solid phase microextraction-gas chromatography–olfactometry

The aroma profile of four cultivars of Viburnum opulus and one cultivar of V. opulus var. sargentii fruits was studied by solid phase microextraction of headspace volatiles and subsequent analysis by gas chromatography, mass spectrometry and olfactometry (SPME-HS-GC–MS–O). In total, 41 compounds were identified, 3-methyl-butanoic acid (63.0–71.8% of identified volatile organic compounds) being the major constituent in the three V. opulus cultivars, while 2-octanone was dominant in one cultivar of V. opulus and in V. opulus var. sargentii, amounting to 28.1% and 25.6% of identified volatile compounds, respectively. Ten odour active compounds were detected and characterised by the trained panel of judges in the course of GC–O by using detection frequency analysis (DFA). 3-Methyl-butanoic and 2-methyl-butanoic acids as well as linalool and ethyl decanoate were found to be the main odour active components for V. opulus aroma.

Identification of Odor-Impact Compounds in Red Table Wines Produced from Frontenac Grapes

Frontenac (Vitis spp. MN 1047) is a recently introduced, cold-hardy red winegrape that is currently the most-planted cultivar in much of the Upper Midwest. Through descriptive analysis, a set of aroma attributes common to red Frontenac table wines has been described, but the volatile compounds responsible for the characteristic sensory notes of the product have not been investigated. In order to identify these odor active compounds, eight Frontenac table wines were evaluated using stir bar sorptive extraction (SBSE) combined with concurrent gas chromatography/olfactometry-mass spectrometry (GC/O-MS). Eight panelists evaluated GC/O effluent using qualitative detection frequency analysis. Twenty-four volatiles were identified in odor regions perceived by panelists, including five alcohols, 14 esters, one lactone, two acids, and two volatile phenols. Twenty-three of these were confirmed by linear retention index data in separate GC-MS analyses, and 23 were quantified in runs using a known concentration of internal standard. Similar analyses of wines produced from V. riparia clone #89, a parent of Frontenac, found 16 volatiles common to Frontenac wines. A brief study of Frontenac juice with two days of skin contact suggested that four volatiles found in the wine may originate in the fruit.

Aroma impact components of Brazilian Cabernet Sauvignon wines using detection frequency analysis (GC–olfactometry)

The aroma profiles of Cabernet Sauvignon wines from a new grape growing region, Santa Catarina State, Brazil, were established for the first time using a Gas-chromatography–olfactometry (GC–O). Two wines were submmited to detection frequency analysis (DFA) ( n = 8), one having vegetative characteristics (SJA wine) and one with red fruits and jam aromas (BR wine) in a prior sensory analysis. Fourteen impact aroma descriptors were selected for judging by DFA analysis. Among these, nine compounds were identified using GC–MS, chromatographic retention times and characteristic odours: acetic acid, butyric acid, isovalerianic acid, 2-phenylethanol, methional, 2-methoxy-3-isobutylpyrazine (MIBP), β-damascenone, β-ionone and furaneol. In most, furaneol was associated with jam or caramel aroma by GC–O and its average concentrations in BR wines (252 μg/l) were significantly higher than those in SJA wine (112 μg/l). In contrast, the amount of MIBP, reported as vegetative or bell pepper aroma by GC–O analysis, was much higher in SJA (0.040 μg/l) than BR (0.018 μg/l) wine samples. In the two wines evaluated, β-damascenone was measured at concentrations that are probably responsible for positive fruity notes and by to mask the vegetal aroma of MIBP in BR wine sensory analysis.